1. Field of the Invention
The present invention relates to an underwater lamp incorporating a solid state lighting element as a light source.
2. Description of Related Art
In recent years, light emitting diodes (LEDs) have been widely used as a light source in underwater applications such as swimming pools, water fountains, rearing ponds, and aquariums.
A typical underwater lamp includes a shell, a lens, and at least one LED. The lens couples to an opening of the shell to seal the shell. Thus the shell and the lens define a hermetic space for receiving the LED therein. The LED includes an LED die facing the lens and a packaging layer encapsulated the LED die. The packaging layer is usually made of transparent macromolecular materials, such as epoxy resin and silica gel. A refractive index of the packaging layer is about 1.5. However, the air between the packaging layer and the lens has a refractive index about 1.0. Snell's Law describes the relationship between the angles and the velocities of the waves. A critical angle is about 42 degree. In other words, the light with an angle of incidence smaller than 42 degrees can pass across the boundary to the space, whilst the light with an angle of incidence not smaller than 42 degrees generates total reflection at the boundary and then travels back to the packaging layer. Only a small portion of the light can pass through the packaging layer into space, and then travels through the lens to the outside. Thus, a utilization efficiency of the light of the LED is relatively low.
Therefore, an improved underwater lamp is desired which overcomes the above-described deficiencies.